The present invention relates to rotary disk storage devices such as magnetic disk devices or a magneto-optic disk devices. In particular, the invention relates to a rotary disk storage device having a stopper which comes into abutment against an actuator assembly to restrict an excessive movement, of the actuator assembly, to an inner or an outer side.
A magnetic disk device as a rotary disk storage device includes a rotary magnetic disk having a magnetic layer formed on a surface thereof and being adapted to rotate about a spindle shaft, a suspension assembly, an actuator assembly, and a control unit for controlling read and write of data and the operation of the actuator assembly.
A slider is attached to the suspension assembly. The slider, to which a magnetic head for read and write of data is attached, provides an air bearing surface (ABS). The actuator assembly includes a carriage arm to which the suspension assembly is connected and which is adapted to turn about a pivot shaft.
A coil arm is formed in part of the carriage arm and holds a voice coil. The coil arm is disposed within a magnetic field of a voice coil magnet. The voice coil magnet and the voice coil constitute a voice coil motor (VCM) which generates a driving force for rotating the carriage arm.
As the magnetic disk rotates, an air current on its surface forms an air bearing, imparting buoyancy to the air bearing surface of the slider and lifting the slider slightly from the magnetic disk surface. The slider turns about a pivot shaft in a state of floating slightly from the magnetic disk surface by the driving force of the voice coil motor, thereby permitting the magnetic head to read and write data in a predetermined position of the disk surface.
With a view to preventing the magnetic disk from becoming unable to turn due to mutual sticking of the magnetic head and the magnetic disk and preventing the resultant damage of the disk and the head, the disk devices adopt a CSS (Contact Start Stop) method and a load/unload method. The CSS method ensures that the magnetic disk surface is made uneven in only a specific area and the magnetic head is retracted to the specific area when the rotation of the disk is stopped. The load/unload method provides a ramp for isolating the magnetic head from the magnetic disk when the rotation of the disk is stopped.
Such disk devices are provided with a stopper for restricting a turning range of the actuator assembly. The stopper comes into abutment against a crash point of the coil arm to restrict the above turning range. When it has become impossible to read a track in magnetic signal recording or reproducing operation, it is necessary to move the magnetic head rapidly to the ramp position (in the load/unload method) or to the position of the specific area (in the CSS method) of the magnetic disk, or when the power supply is interrupted suddenly, it is necessary that the magnetic head be moved to the ramp position (in the load/unload method) or to the position of the specific area (in the CSS method) of the magnetic disk by utilizing a counter electromotive force of the disk. In order to prevent rebounding of the actuator assembly under a collision shock of the coil arm, the stopper is required to be elastic enough to absorb the shock. At the time of writing a servo pattern as track positioning information onto the magnetic disk, the stopper is also required to function as a reference for determining a write position and is therefore required to have a certain degree of rigidity.
In connection with such a stopper there is known, for example, a disk device (see, for example, Japanese Patent Laid-open No. 9-55047) wherein an inner stopper adapted to define an innermost periphery to which a slider with a magnetic head attached thereto is movable on a magnetic disk surface, and an outer stopper adapted to define an outermost periphery to which the slider is movable, are provided at both end portions of a turning range of a coil arm.
In the disk device disclosed in the above-referenced patent, the inner stopper and the outer stopper are each composed of a shaft fixed to a base of the disk device with an annular groove formed on an outer periphery surface thereof, and a cylindrical shock-absorbing rubber mounted on the shaft so as to cover the annular groove. In such inner and outer stoppers, even if there is used a shock-absorbing rubber having a high hardness, the cylindrical shock-absorbing rubber deflects while getting into the annular groove and therefore can absorb the shock of the actuator assembly.
As the stopper used in the magnetic disk device there also is known a stopper constituted by only an elastic member such as rubber. In this stopper, the shock of the actuator assembly is absorbed by only the elastic function of the elastic member.
However, in the disk device disclosed in the above-referenced patent, a stopper shaft is disposed on the track of a crash point of the coil arm, so in assembling an actuator and at the time of installing the magnetic disk in a housing, mounting a lower yoke, and further mounting the actuator and an upper yoke as an integral combination to the housing, it is necessary to turn the actuator up to a position beyond a fixed position of the outer stopper so as not to overlap the magnetic disk in a planar position, or else it will become difficult to effect assembling of the actuator. Besides, the actuator and the magnetic disk are overlapped at the fixed position of the outer stopper in a planer manner. Therefore, even if the cylindrical shock-absorbing rubber is removed from the shaft, the assembling of the actuator may become difficult as long as there is such an actuator-disk overlapped condition. Even in the case where the overlapped condition is eliminated by removing the cylindrical shock-absorbing rubber from the shaft, since both inner and outer stoppers are installed between the lower yoke and the upper yoke, it is necessary to assemble the lower yoke, actuator, cylindrical shock-absorbing rubber, and upper yoke in this order, resulting in the complicated assembling-work. Further, since the cylindrical shock-absorbing rubber is formed thin enough to get into the annular groove and deflect, a magnetic member such as a permanent magnet which can attract the coil arm has so far been unable to be embedded in the cylindrical shock-absorbing rubber.
On the other hand, in the case of a stopper constituted by an elastic member alone, the stopper can be provided only in an operation angle range of the coil arm of the actuator assembly. Besides, since a magnet is embedded in the elastic member, the volume of the elastic member is limited and it has heretofore been impossible to let the elasticity of the elastic member be exhibited efficiently. If a pin or the like is disposed nearly centrally of the elastic member for fixing the stopper in question, the volume of the elastic member decreases and here again it has so far been impossible to let the elasticity be exhibited efficiently.
Moreover, the stopper constituted by an elastic member alone is poor in mounting stability and involves the drawback that its portion of abutment against the coil arm is displaced and causes a change in the turning range of the actuator assembly. Further, since this stopper has a dislodgment preventing pawl in its inserting portion, is directly inserted into a hole and is established its position, the inserting resistance becomes large, causing a working drawback such that the use of a lubricant is essential for smooth insertion. Additionally, this positioning cannot be done accurately and a start point of data write becomes uncertain.